The present invention relates to process control and measurement. More specifically, the present invention relates to a handheld field maintenance tool for use in conjunction with process control measurement systems.
Handheld field maintenance tools are known. One example of such a device is the Model 275 Highway Addressable Remote Transducer (HART) communicator. The HART communicator is a handheld tool that provides a common communication link to all HART-compatible, microprocessor-based field instruments (or process devices). The HART communicator interfaces with HART compatible devices and communicates using the Bell 202 frequency shift key (FSK) technique of providing high-frequency digital signals superimposed on a standard transmitter current loop of 4–20 mA. The HART communicator provides a number of known diagnostic and communication functions which facilitate maintenance of the process devices. In fact, the HART communicator can streamline regulatory documentation preparation through access to historic configuration and as found/as left data. While the HART Model 275 communicator is recognized as a valuable asset to the maintenance of process control instrumentation, it is slightly limited in one regard. Specifically, the Model 275 can only be used in conjunction with HART-compatible process devices. Additional tools are also available for other process industry protocols, but to date, no one has provided an effective handheld tool that can be used in conjunction with process industry protocols having different physical layer specifications.
In a process control installation employing process devices communicating in accordance with varying physical layer specifications, maintenance technicians would be forced to carry multiple protocol-specific handheld tools to interact with each and every device of a distinct protocol. While such a situation is undesirable, the solution is either to standardize upon a single process industry protocol, or work with one set of process industry protocol devices at a time.
A handheld field maintenance tool that could operate on different process communication loops having differing physical specifications would facilitate process device maintenance and allow a technician to access varying devices without the necessity of having to carry around multiple handheld tools. One of the primary technical hurdles to building such a tool is the different physical layer specifications themselves. For example, a handheld tool adapted to communicate in accordance with one physical layer specification may actually cause damage if employed upon a process control loop requiring a different specification. A handheld tool that solves the above technical hurdles and provides use for different physical layer specifications would vastly simplify the maintenance of process control devices.